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Topic: Question about stretchy 350W SiC deck (Read 277 times)

I am back at the shortwave transmitter again. I've had it working great below 4 MHz, but now I am back to trying to make it work higher again. I thought I had it at 87% efficiency, but I looked on a spectrum analyzer and it's terrible. When I run it next to the filter, then it's great, but only 76% efficiency @ 6.8 MHz. I am almost 100% sure it has to do with my broadband output match.

Anyway, I'm thinking about buying your SiC RF deck. The 350W one with 4 fets I believe. How much would that cost?

I know you use those T200-2s. What else do you have to match the output beside the transformer?Yours is not wideband, right? you have to tune it to the band?

Funny you should ask as have just sold one last week (just the generator), PM me for prices!

I no longer use the SiC FETs and have gone GaN as they're much easier to drive.

I'll have a root around as I'm sure I've got an older quad SiC somewhere, let me know what 16 freqs you want so I can program and test it for you. (6-7MHz ONLY)

The T200 tran is just 1:1 and sets the impedance of the O/P stage, more turns = less I and Higher Z.

You conjugate match whatever Z using series L and parallel C, very simple.

Mine's set for 5R as I'm using 48V 10A (4R8!), a higher Z would be much better (using a higher voltage of course) and efficiency would also improve because of less I2R loss.

I had tried different matching methods but the one I use is the simplest, most compact and most efficient design I tried.

It's class E so not wideband but it's kinda D/E and can get 1 MHZ B/W at 40m which is plenty, it's a single band design after all and have no intention of switching in seperate LPF's etc..

Changing band wise you'd have to use different material on the T200's if you went lower as you'd need more turns (no room left!) to keep the Z, maybe use thinner wire but the PTFE silver plated stuff I use is fairly thick and already getting warm!

Fine if you want to go higher (GaN ONLY) and have one working at 14MHz.

So thinking aloud here.............. I have a Quad SiC cased up for testing (can't check as I'm away from home, back Friday) somwhere I think.......................Will need a HS bolting to the case tis all...